ADRIA, an expert laboratory for the validation of rapid microbiological methods

To reduce microbiological testing times, food manufacturers may use rapid test kits. However, these methods must demonstrate performance equivalent to that of standardised reference methods. ADRIA supports diagnostic solution providers during the final stages of rapid method development. As an internationally recognised expert laboratory, ADRIA conducts validation studies of alternative microbiological methods for certification under NF VALIDATION (AFNOR), MicroVal and AOAC-RI schemes.

Validation of alternative methods: what do the regulations require?

Under European regulations, food business operators are responsible for the safety and suitability of the products they place on the market. They must comply with the microbiological criteria established by Regulation (EC) No 2073/2005. This Regulation provides for the use of standardised reference methods or validated alternative methods to assess compliance with these criteria.

The ISO 16140 series of standards, and particularly ISO 16140-2:2016, defines the protocol for the validation of alternative commercial methods used in food microbiology. A validation study determines a method’s performance characteristics and provides evidence of its equivalence to a reference method.

An ISO 16140-2 validation study is initiated by diagnostic solution providers. However, to be recognised by certification bodies such as NF VALIDATION or MicroVal, it must be conducted by an independent expert laboratory such as ADRIA.

How are alternative method validation studies conducted?

Validating a method means demonstrating that its performance meets a defined objective. For example, a method designed to detect Salmonella in food intended for human consumption must be capable of detecting a single cell in a sample.

For an “alternative” method, the validation study must also demonstrate that its performance is equivalent to that of a “reference” method applied in parallel to comparable samples. Reference methods are generally published as national or international standards.

The protocol described in ISO 16140-2:2016 for the validation of alternative methods consists of two phases: a method comparison study and an interlaboratory study. The performance characteristics assessed differ depending on whether the method is qualitative or quantitative.

Qualitative methods are characterised by their sensitivity and level of detection. Sensitivity assesses a method’s ability to detect the target micro-organism under challenging conditions, for example in the presence of growth inhibitors or PCR inhibitors, or when the target is present at a very low level or has been stressed.

The level of detection (LOD) corresponds to the minimum contamination level that the method can detect with a given probability, generally 50%. The LOD is compared with that of the reference method to determine the relative level of detection (RLOD).

Quantitative methods are characterised by their relative trueness and accuracy profile. Relative trueness assesses the closeness between the counts obtained using the two methods. The accuracy profile demonstrates that the bias of the alternative method remains within acceptable limits, regardless of the contamination level of the food product.

For both types of methods, inclusivity and exclusivity are also assessed. Inclusivity is the ability to detect or enumerate the target micro-organism while taking its taxonomic diversity into account. Exclusivity is the ability to avoid false-positive results caused by non-target micro-organisms.

The method comparison study is conducted entirely by the expert laboratory. The interlaboratory study involves the expert laboratory and collaborating laboratories representative of the diversity of laboratories operating at national, European or international level.

These laboratories apply the method to identical samples in order to characterise the variability that may occur under normal conditions of use.

Why choose ADRIA for the validation of alternative methods?

Since the late 1990s, ADRIA has supported the diagnostic industry in validating rapid microbiological testing methods. ADRIA is now an independent, internationally recognised expert laboratory conducting validation studies for NF VALIDATION, MicroVal and AOAC-RI certification schemes.

ADRIA’s expertise in method validation is based on three key strengths:

• A skilled and qualified technical team working in a comprehensive microbiology laboratory structured to ensure the traceability of analyses from sampling through to the final test report. The laboratory’s performance and its ability to conduct tests using standardised reference methods are recognised through accreditation (COFRAC Testing No. 1-0144, scope of accreditation available at www.cofrac.fr).
• A culture collection comprising more than 4,700 strains of bacteria, yeasts and moulds. Most of these strains have been isolated from food products or food production environments and characterised using molecular methods.
• An approach focused on the quality and scientific relevance of validation studies. ADRIA reproduces realistic contamination scenarios and challenging conditions in order to demonstrate the suitability of a method for use in an industrial environment.

To contribute to exchanges between stakeholders involved in method validation, ADRIA actively participates in the NF VALIDATION and MicroVal technical committees, as well as the AFNOR V08B standardisation committee for food microbiology.

To share its long-standing experience at international level, ADRIA also appoints experts to represent France through AFNOR within ISO working groups, including:

• ISO/TC 34/SC 9/WG 3 “Method validation”
• ISO/TC 34/SC 9/WG 19 “Guidelines for conducting challenge tests”
• ISO/TC 34/SC 9/WG 16 “Yeasts and moulds”
• ISO/TC 34/SC 9/WG 25 “Whole-genome sequencing for typing and genomic characterization”.